While it works great for the vinyl player input, it doesn't work at all for the computer input . In this latter case, a jack-to-RCA cable is the input in my RCA switch.

I think it's a ground problem. It's worth knowing that in my circuit I have wired all RCA negative poles to the same ground node by a plastic wire connector. Do you think it's the way to proceed? Do you have any other idea about the cause of the problem?

I think it's a ground problem. It's worth knowing that in my circuit I have wired all RCA negative poles to the same ground node by a plastic wire connector. Do you think it's the way to proceed? Do you have any other idea about the cause of the problem?

It's standard to connect all the shield/ground tabs on the jacks together, and just switch the 'hot' or 'signal' lines.

Do you have a wire with alligator clips on each end? Bypass the switch by connecting the computer 'IN' signal (RCA center conductor) to the 'OUT' jack with your test wire.
Or, use a female-female RCA connector to connect the RCA computer cable to the amplifier cable...
Or plug the computer cable directly into the amp
Does it work / play music? If 'Yes' then it is a switch connection problem.
If 'No', then check your computer 'Out' connection,and soundcard settings to make sure you are pumping signal out of the computer.

Check the switch connections with a test light or multimeter (needle-type) on OHMs to make sure the switch is working the way you think it is.

You can figure this out- just be logical.

Oh, and PLEASE do a better wiring job than the other builder did, as the picture shows. You don't need all those big loops of wire jumbled together in your box!

I would be a bit concerned if you are switching the low-level signal from a turntable and the (higher) line output from a computer or CD player - be careful to set the levels properly.
John

PS- By plastic wire connector, you mean a 'wire nut' aka Marr connector? That's OK for testing, but better to solder wire from jack to jack, connecting the 'ground'/'negative' tabs. Depending on the jack spacing sometimes you can solder the tabs from a pair to each other.

ABou -- What victoria guy says about the leignth of wires in the example (first post) is true. The switch box as built should not work well because of construction technique. Also use metal boxes for this kind of thing. Shielding is your friend.